NYC83FU010

According to the plt, the registered ultralight acft was brought to a field during the morning to check out the control rigging & to familiarize him with the vehicle. There was no intention to fly the ultralight at that time. Later in the day, the plt was taxiing & 'crow hopping' in north & south directions. A witness reported that while it was proceeding in a northerly direction, the ultralight made several hops in the air. He reported that it then veered in a westerly direction, hopped up & down & finally became airborne. It climbed above tree top level, then turned left as if the plt was returning to the field. However, while in a turn, the left wing collided with the tree tops & the ultralight cartwheeled & crashed. The plt was seriously injured & could not remember details of the accident.